The present invention relates to an isolator device with a high frequency power amplifier circuit and an isolator element, used in for example a transmitting section of a portable phone or a mobile communication terminal.
Recently, competition for downsizing and weight reduction of communication devices such as portable phones and mobile communication terminals has become intense and thereby, requests for further decrease of parts constituting these communication devices in size, weight and thickness, quantity, and power consumption have been raised more and more.
In a communication device such as a portable phone and a mobile communication terminal, an isolator element serving as an non-reciprocal circuit element is generally connected to an output side of a high frequency power amplifier circuit in a transmitting section in order to hinder the high frequency power reflected due to conditional variations of an antenna from reaching the high frequency power amplifier circuit by an isolator element and to prevent the high frequency power amplifier circuit from deteriorating or unnecessary outputs from increasing.
A conventional high frequency power amplifier circuit is formed on a dielectric substrate as a module and mounted in a metallic case for shielding. In the case of an isolator element, on the other hand, it is necessary to cover a magnetic material with a high magnetic permeability metal because of the structure of the element. Therefore, because it is different from normal electronic circuits formed on an insulating substrate in material and structure, the isolator element is fabricated as an independent component. That is, a conventional isolator element is mounted in a metallic case separate from a high frequency power amplifier circuit.
Thus, although a high frequency power amplifier circuit and an isolator element are deeply related with each other in function, they are handled as components separate from each other until they are set in a portable phone or mobile communication terminal. That is, these high frequency power amplifier circuit and isolator element are prepared as independent components and then mounted by soldering on a motherboard constituted of a dielectric multi-layered substrate.
Since the high frequency power amplifier and the isolator element are handled as independent components, it is difficult to decrease them in size. Thus, when they are mounted on the motherboard, the thickness of the motherboard and that of the isolator element are added each other causing the total height to increase, so that it is impossible to decrease the whole high frequency-output stage in size and thickness.
Every port of an isolator element is fabricated so that its input/output impedance becomes 50xcexa9 which is the standard transmission-line impedance but the output impedance of a high frequency power amplifier circuit is 30xcexa9 or less. Therefore, to connect a high frequency power amplifier with an isolator element, it is necessary to use an impedance matching circuit. Such impedance matching circuit is provided by mounting chip components of L and C on a motherboard or by forming L of a copper film pattern on the surface of the motherboard. The impedance matching circuit having the above configuration also prevents the high frequency output stage from decreasing in size and thickness.
It is necessary to separately obtain such components as a high frequency power amplifier circuit and an isolator element and also to separately design an impedance-matching circuit for coupling them. Thus, it is complicated to design a communication device such as a portable phone or a mobile communication terminal and variations of individual components is to be considered. Therefore, it may not be possible to assure keeping of performance over the whole communication device.
It is therefore an object of the present invention to provide an isolator device with a built-in power amplifier making it possible to greatly decrease a high frequency output stage in size and thickness.
It is another object of the present invention to provide an isolator device with a built-in power amplifier making it possible to easily design a communication device such as a portable phone and a mobile communication terminal, and to minimize variations in performance over the whole communication device.
According to the present invention, an isolator device with a built-in power amplifier includes a single dielectric multi-layered substrate, a high frequency power amplifier circuit, an isolator element, and circuit elements provided to the dielectric multi-layered substrate. The high frequency power amplifier circuit and the isolator element are connected with each other through the circuit elements and united with the single dielectric multi-layered substrate.
As described in detail, according to the present invention, a high frequency power amplifier circuit and an isolator element are connected with each other through circuit elements provided to a single dielectric multi-layered substrate and also united with the single dielectric multi-layered substrate. Since a high frequency output stage is united with the single dielectric multi-layered substrate, it is possible to greatly decrease the high frequency output stage in size and thickness. Also, it is possible to reduce the number of components due to the unification.
The isolator device with built-in power amplifier according to the present invention has advantages of (1) reducing the mounting area of the whole high frequency output stage, (2) reducing the design labors of communication devices because a designer of the communication device such as a portable phone and a mobile communication terminal needs not to separately obtain components such as a high frequency power amplifier circuit and an isolator element or separately design an impedance matching circuit for connecting these components, and (3) minimizing the performance variations over the whole communication device.
It is preferred that at least a part of the circuit elements is embedded in the dielectric multi-layered substrate. Also, it is preferred that the circuit elements include a capacity section of the isolator element, and that the capacity section of the isolator element is embedded in the dielectric multi-layered substrate.
It is further preferred that at least a part of the circuit elements is mounted on the dielectric multi-layered substrate.
Preferably, an impedance matching circuit for matching an output impedance of the high frequency power amplifier circuit with an input impedance of the isolator element is embedded in the dielectric multi-layered substrate, or mounted on the dielectric multi-layered substrate.
It is preferred that a main part, more concretely a circulator element and center conductors, of the isolator element is integrally inserted into a fitting section formed by removing a part of the dielectric multi-layered substrate. This fitting section may be a cutout or a via hole of the dielectric multi-layered substrate. Since the main part of the isolator element is integrally inserted into the fitting section as the cutout or via hole. it is possible to unite the high frequency power amplifier circuit and the isolator element into one body without increasing the overall height, and to decrease the body in thickness.
It is preferred that the isolator element has a first port electrically connected to the high frequency power amplifier circuit through an impedance matching circuit, and that the first port has a standard transmission-line impedance.
It is also preferred that the isolator element has a first port electrically connected to the high frequency power amplifier circuit, and that the first port has an input impedance almost matched with an output impedance of the high frequency power amplifier circuit. In this case, preferably, the first port of the isolator element is electrically connected to the high frequency power amplifier circuit through an impedance matching circuit. Since the impedance of the input port of the isolator element, connected to the high frequency power amplifier circuit, is adjusted to an impedance close to the output impedance of the high frequency power amplifier circuit, the impedance-matching circuit is simplified and it can be further decreased in size.
It is preferred that the isolator element has a second port having an impedance different from the impedance of the first port. In this case, more preferably, the impedance of the first port is lower than the impedance of the second port.
The impedance of the second port may be equal to a standard transmission-line impedance.
It is preferred that the circulator element includes a magnetic material block and trigonally symmetric center conductors formed in the magnetic material block, and that a width of the center conductor connected to the first port is different from a width of the center conductors connected to other ports.
It is also preferred that the isolator element has a circulator element, an upper surface of the circulator element being in almost the same plane as an upper surface of the dielectric multi-layered substrate, and that terminal electrodes of first and second ports of the circulator element are positioned at the upper surface of the circulator element.
It is further preferred that the isolator element has a circulator element, an upper surface of the circulator element being in almost the same plane as an upper surface of the dielectric multi-layered substrate, and that terminal electrodes of first and second ports of the circulator element are positioned at the upper surface and a lower surface of the circulator element, respectively.
It is preferred that the high frequency power amplifier circuit and the isolator element are covered by a common single shielding case made of a soft magnetic material such as iron or the like, so that all functional members in the isolator device are shielded and a closed magnetic circuit is formed around the entire isolator device to completely exhibit functions of the isolator device.
It is also preferred that the device further includes an SAW (surface acoustic wave) device mounted on the dielectric multi-layered substrate and coupled to an input of the high frequency power amplifier circuit, and a matching circuit embedded in or mounted on the dielectric multi-layered substrate to match an output impedance of the SAW device with an input impedance of the high frequency power amplifier circuit.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.